Method of forming a suspension for use in a disk drive having a media disk

ABSTRACT

A suspension for use in a disk drive is disclosed. The suspension has a hinge and load beam which are separately formed and subsequently joined together. The load beam is formed from a material which has improved damping characteristics. The load beam additionally has ribs constructed in order to balance the mass of the suspension about the torsional rotation axis. The location of the torsional rotation axis can be designed to intersect the head gimbal pivot point.

RELATED APPLICATIONS

This Divisional Application claims the priority of Parent applicationSer. No. 09/939,074 , now U.S. Pat. No. 7,054,109 filed on Aug. 24,2001, and entitled “Balanced and Damped Suspension for Use in a DiskDrive.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to magnetic disk drive technology, andmore specifically to a suspension for use in a data storage disk drive.

2. Description of the Background Art

Disk drives are used for nonvolatile memory storage in computer systems.Disk drives have at least one magnetic recording head mounted on aslider. An actuator positions the slider over a magnetic disk forwriting and reading information on the disk. The mechanism whichconnects the slider to the actuator is called a suspension. Conventionalsuspensions have several shortcomings including poor dampingcharacteristics and other characteristics which contribute to increasedtrack misregistration (TMR) as discussed in detail below. The presentinvention is a suspension which has superior damping characteristics andoptimized TMR performance.

Some of the features of conventional suspensions are illustrated inFIGS. 1 a and b. Most suspensions have a mounting plate 102 having ahole 104 with a raised lip (not shown) for swaging into a rigid arm. Thesuspension has a hinged portion 106 and a rigid load beam portion 108.The hinge portion 106 imparts a spring action to the load beam 108 whichforces the slider toward the disk. Each load beam has an associated headgimbal pivot point. There are at least two head gimbal structures usedin suspensions which differ in the slider attachment to the suspension.The location of the head gimbal pivot point depends on which of thesestructures is used. For the structure illustrated in FIGS. 1 a and b,the slider 110 is attached to a flexure 112 forming a head gimbal whichis also called a slider gimbal. In this structure, there is a dimple(not shown) usually formed on the load beam which serves as the pivotpoint for the head gimbal. The dimple may also be formed on a flexuremember which is attached directly to the load beam. The location of thedimple establishes the head gimbal pivot point relative to the loadbeam. Another type of suspension does not use a dimple to define thehead gimbal pivot point and is known as a dimpleless design. This designis taught in U.S. Pat. No. 5,198,945 and U.S. Pat. No. 5,912,788.Referring to FIG. 2, the pivot point for the head gimbal is theintersection of a torsional axis 32 of the flexure and a pitch axis 30.FIG. 3 shows how the head gimbal is constructed to include a load beam.

Referring to FIGS. 1 a and 1 b, a suspension generally has a torsionalvibration mode which rotates about a torsional axis 114. To providestiffness to the load beam 108 a portion of each of the outside edges118 is bent out of the plane of the load beam to form a flange 116 asshown in FIG. 1 a. Most commonly the flanges are bent away from thedisk, but they can also be bent toward the disk. The flat portion 120 ofthe load beam between the flanges 116 defines the plane of the loadbeam. In conventional suspensions the load beam 108 and the hingeportion 106 are formed from the same continuous sheet of material. Theforming process for hinge portion 106, which produces spring action,alters the relative position of the load beam portion 108 to themounting plate 102. Two parameters of this relative position are sag andformed area flatness (FAF), which are described in detail below.

An important index of the performance of a disk drive is trackmisregistration (TMR). Track misregistration is a measure of thedistance from the recording head to the center of the desired track onthe disk and represents an undesired misalignment of the head withrespect to the center of the track. As the offset of the torsional axisof the suspension increases relative to the pivot point of the slidergimbal the TMR also increases. This is because the offset of thetorsional axis to the pivot point of the slider acts as a lever forlateral slider motion. This lateral motion contributes directly to TMR.

As illustrated in FIGS. 4 a, c, and e (in which the vertical scale isexaggerated), sag is shown as the location or offset of the flat portionof the load beam 403 with respect to the mounting plate 401. The amountof sag in a conventional suspension determines the degree to which thetorsional axis is misaligned with the pivot point of the slider gimbal.FIG. 4 a shows a side view of a suspension with positive sag 410. FIG. 4a includes a view of the mounting plate 401, the hinge portion 402, theload beam portion 403, and the slider 404. A positive sag exists whenthe gimbal pivot point of a suspension is closer to the disk than theaxis of torsional rotation. FIG. 4 b shows an end view of the load beam406, the slider 404 and the pivot point 407 for the case of positivesag. Because of positive sag, the torsional axis 405 is above the slidergimbal pivot point 407 which results in additional movement of therecording head 408 and increased TMR 409. FIG. 4 c shows a case ofoptimal sag 410 wherein the torsional axis intersects the gimbal pivotpoint. This results in minimal TMR 409 and good disk drive performance.In FIG. 4 c, the mounting plate 401, hinge portion 402, load beam 403,and slider 404 are similar as in FIG. 4 a. In FIG. 4 d it is shown thatat optimal sag the torsional axis 405 intersects the pivot point 407.FIG. 4 e illustrates negative sag 410. FIG. 4 f illustrates that fornegative sag the torsional axis 405 is below the pivot point 407resulting in greater movement of the recording head 408 and increasedTMR 409.

The distance between the torsional axis and the pivot point acts as alever arm. Since the slider is constrained by the presence of the diskfrom rotating as it flies on the disk surface, this lever transfers thetorsional motion of the load beam as linear motion to the slider. Thislinear motion is perpendicular to the direction of the recorded track.This sideway linear motion of the slider relates directly to TMR becausethe recording head attached to the slider moves away from the center ofthe track. Therefore, from FIG. 4 a, b, c, d, e, and f, it can be seenthat the farther the torsional axis is away from the pivot point thegreater the effect on TMR. Therefore, it is desirable to keep thedistance between the torsional axis and the pivot point which acts as alever arm as small as possible to minimize TMR.

Another parameter of the suspension which must be controlled is theFormed Area Flatness (FAF). Referring to FIGS. 1 a and 1 b, FAF isdefined as the coplanarity of the flat portion 120 of the load beam withrespect to the mounting plate 102. In other words, FAF is a measurementof the angular tilt of the flat portion 120 of the load beam using themounting plate as a reference surface. FAF and sag are interdependent inconventional suspensions which have the same continuous material usedfor forming both the hinge and the load beam. Generally a conventionalsuspension with optimized FAF will have sub optimum sag and conversely asuspension with optimized sag will have sub optimal FAF. FAF primarilycontrols how much power, or gain, is in the torsional vibrations of thesuspension whereas sag primarily controls the effect of torsionalvibrations on TMR. The effects of both FAF and sag are important factorsin the dynamic performance of the suspension.

What is needed is a suspension in which the sag can be controlledindependently from FAF and the hinge forming process. For the torsionalvibrations that do occur, it is desired to have the gain of thosevibrations substantially reduced by the damping characteristics of thesuspension.

SUMMARY OF THE INVENTION

One aspect of the present invention provides for a suspension in whichthe sag is independent from FAF. This is accomplished by fabricating theload beam separately from the hinge. Another aspect of the invention isto provide for a load beam constructed from a material which has greatlyimproved vibration damping characteristics. A suspension embodying theinvention has improved damping. A disk drive using a suspensionembodying the invention has improved TMR performance.

In one embodiment, the suspension has a hinge and a load beam fabricatedseparately and subsequently joined together. The load beam has anassociated head gimbal pivot point. The load beam also has a torsionalaxis which passes approximately though the pivot point. The load beamhas one or more ribs formed such that the distribution of mass of theribs when combined with the distribution of mass of other portions ofthe load beam result in the balance of the total mass about thetorsional axis. By separately forming the load beam and the hingeportion, the load beam can be formed from a material with superiordamping characteristics without compromising the spring action of thehinge.

In another embodiment of the invention, a disk drive is fabricated usinga suspension with a load beam and a hinge fabricated separately. In thisembodiment a disk drive thus constructed has improved trackmisregistration.

Briefly and in general terms a suspension according to a preferredembodiment of the invention has a hinge and a load beam fabricatedseparately. This allows FAF to be adjusted at the time of fabricatingthe hinge without affecting sag. In addition the load beam can be formedfrom a material with superior damping characteristics. Other aspects andadvantages of the present invention will become apparent from thefollowing detailed description which taken in conjunction with thedrawings illustrate by example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a drawing of the top side of a prior art suspension;

FIG. 1 b shows a drawing of the bottom side (adjacent to the disk) of aprior art suspension;

FIG. 2 shows details of a dimpleless suspension;

FIG. 3 shows a dimpleless head gimbal apparatus;

FIG. 4 a shows a side view of a suspension which has positive sag;

FIG. 4 b shows an end view of a suspension which has positive sag;

FIG. 4 c shows a side view of a suspension which has optimum sag.

FIG. 4 d shows an end view of a suspension which has optimum sag;

FIG. 4 e shows a side view of a suspension which has negative sag;

FIG. 4 f shows an end view of a suspension which has negative sag;

FIG. 5 a shows a cross sectional drawing of a disk drive;

FIG. 5 b shows a top down drawing of a disk drive;

FIG. 6 illustrates an embodiment of the present invention;

FIG. 7 shows the cross section profiles of the load beam featuresincluding the mass balancing ribs;

FIG. 8 a shows an end view of one embodiment of the load beam features;

FIG. 8 b shows a side view of one embodiment of the load beam features;and,

FIG. 9 shows a detailed view of the mass balancing ribs.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the present invention the load beam and the hingeare fabricated separately and subsequently joined together. This allowsthe FAF to be controlled with the hinge forming process separately fromsag. In another embodiment the load beam is formed from a material whichis more efficient at damping vibrations. In addition the load beam canhave ribs or other features formed to balance the mass about the desiredlocation of the torsional axis. This enables the location of thetorsional axis to be placed to approximately intersect the pivot pointand thus minimize TMR. In previous suspensions the load beam and thehinge were generally formed from one continuous sheet of material. Thematerial was thus selected for the spring properties required for thehinge. These materials, typically a stainless steel, generally havelimited vibration damping characteristics. In previous suspensions theFAF could not be controlled without affecting the sag.

FIGS. 5 a and b illustrate some of the components of a disk drive usedfor magnetically storing digital data. One more magnetic disks 502 withrecording surfaces are connected with hub 506 and drive motor 504. Themotor 504 rotates the disks during normal drive operation. Some diskdrives are designed such that the slider 510 comes to rest on the diskwhen the disk drive is stopped. In other disk drives, the slider islifted off the disk surface when the disk drive is turned off. Theembodiments of this invention apply to both load/unload and start/stopapplications.

A magnetic recording head assembly 508 is formed on the trailing surfaceof a slider 510 and is used for reading and writing digital data on therecording surface of the disk. The recording head assembly usuallycomprises a separate write element along with a separate read element.The slider 510 is connected to an actuator 512 by means of a rigid arm514 and a suspension 516. The suspension 516 provides a force whichpushes the slider toward the surface of the recording disk 502.

FIG. 6 shows a perspective view of a mounting plate and load beamcombination 600 according to an embodiment of the present invention. Themounting plate 604 is attached to the hinge portion 606. The hingeportion 606 is formed as a separate member. After fabrication, the hingeportion 606 and the load beam 602 are joined as indicated in theexploded view in FIG. 6. Flanges and ribs formed on the load beamincrease the rigidity of the load beam so that the spring force of thehinge can be more efficiently transferred to the pivot point 612.Rigidity can also be increased by increasing the thickness of the loadbeam material; however, this has the disadvantage of increasing the massof the load beam. By appropriately selecting the height, location, andsize of flanges and ribs, the mass of the load beam can be distributedequally and in a balanced manner about the desired torsional axis of thesuspension.

Depicted in FIG. 6 is a load beam 602 which has flanges 610 formed in aportion of the outside edges. There are also one or more portions of theoutside edges of the load beam which are formed into ribs 608. Shapesother than flanges and ribs can be formed to achieve similar results ofstiffening and balanced mass distribution. An alternative embodiment isto place one rib in the central portion of the load beam. It is alsopossible to add additional material to form the ribs. Although thiswould accomplish the purpose of balancing the mass, the total mass woulddisadvantageously increase.

For a suspension which has flanges 610 formed toward the disk, the ribs608 generally extend above the plane 616 of the load beam 602 and awayfrom the disk. Conversely, for a suspension which has flanges 610 formedaway from the disk, the ribs 608 generally extend blow the plane 616 ofthe load beam 602 and toward the disk. Preferentially the load beam hasa dimple 612 which applies a load or force to the slider, urging theslider towards the disk. However the dimple could also be formed on aseparate member and attached to the load beam. A dimpleless suspensionmay also be used. The load beam has an optional load/unload tab 614 ifthe suspension is to be used in a load/unload application.

A view of one embodiment of a load beam 602 is shown in FIG. 7. Asindicated in FIG. 7, a cross section 702 through the ribs indicated bythe A-A line is shown. Also a cross section 704 through the flanges asindicated by the B-B line is shown. In the embodiment shown in FIG. 7,the distribution of mass from the flanges 706 is predominately downwardand the distribution of mass from the ribs 708 is predominately upwardrelative to the plane of the suspension 716. If the ribs were notpresent, the torsional axis would pass above the pivot point asexemplified in FIGS. 4 a and b. By constructing ribs, the position ofthe torsional axis is shifted upward toward the pivot point. Acombination of the height, length, and width of the ribs are chosen sothat the torsional axis passes through or in close proximity to thepivot point.

The preferred construction of the ribs 708 and flanges 706 is shown inthe end view presented in FIG. 8 a. The embodiment of the suspensionshown in FIGS. 8 a and b has a dimple 806 to define the slider pivotpoint. However a dimpleless suspension can also be utilized. Forreference, a side view of the suspension in FIG. 8 a is shown in FIG. 8b.

FIG. 9 also shows details of shape and structure of the ribs 902according to an embodiment of the present invention. Two small optionalholes 904 have been added at each end of each rib for stress relief ofthe material during the forming process. An expanded view of the lifttab 906 of this suspension is also shown. Although the primary purposeof the ribs is for balancing the mass of the suspension, a secondary usecan be for assisting with assembly into the drive. The ribs can be usedas contact surfaces for tooling that will hold adjacent head pairs apartas they are inserted between disk surfaces.

As discussed earlier, conventional suspensions use the same contiguousmaterial for both the hinge portion and the load beam portion. It is arequirement that the hinge portion have a spring action which urges theload beam toward the disk surface. Consequently the material in mostcommon use is chosen for the spring characteristics and is usually astainless steel, such as stainless 301 or 302, for the contiguous hingeand load beam. However stainless steel is not efficient at dampingvibrations compared with other materials. In accordance with the presentinvention the load beam is made of another material since it is formedseparately from the hinge portion. Using a non-spring material for theload beam chosen to enhance vibration damping thus results inenhancements to suspension performance. Accordingly, a load beam can beconstructed that is lighter, stiffer and in particular has improveddamping characteristics compared with a conventional load beamconstructed with spring material. Suitable materials may be selectedfrom metals, plastics, or ceramics for the load beam. The preferredmaterial is magnesium or a magnesium rich alloy. Magnesium is known forits intrinsic damping properties and has the added benefit of being lessthan half as dense as stainless steel. A magnesium or magnesium alloyload beam can be attached to the hinge by several methods. Some of thesemethods include, but are not limited to, adhesive bonding, diffusionbonding, or a pretreatment of the surface which enables welding. Thepreferred attachment method is a pretreatment of the magnesium surfacewith a nickel layer which allows for conventional welding. A nickellayer also increases the stiffness of the magnesium load beam. Usingknown techniques to apply nickel on magnesium or magnesium alloy resultsin a suspension that is stiffer than a conventional suspension made ofstainless steel. A load beam with a magnesium core and a nickel outerskin is not only stiffer but is also lighter, and has better dampingthan a convention stainless steel load beam of equivalent thickness.Also by constructing an outer skin of nickel to the appropriatethickness, the coefficient of thermal expansion of the load beam ismatched to that of the attached steel hinge.

An alternate embodiment of this invention is to form a load beam from asheet of a constrained layer damping material. A sheet of constrainedlayer damping material is a sandwich of a viscoelastic material disposedbetween two sheets of metal. A typical configuration is a layer ofviscoelastic material similar to that supplied by 3M under the productname Damping Polymer 242F01. A typical thickness of the viscoelasticmaterial is 0.001 inch. This viscoelastic material is sandwiched betweentwo sheets of 301 or 302 stainless steel. The thickness of the stainlesssteel depends on the desired stiffness and mass. For typicalapplications the stainless steel thickness is approximately 0.0015 inch.The entire load beam is constructed from this constrained layer dampingmaterial. This laminated material is die cut and formed into a load beamby conventional stamping and forming techniques. An advantage of thisembodiment is that the entire load beam is constructed from theconstrained layer damping material. A disadvantage of this embodiment isthat the load beam stiffness will be less than a conventional allstainless steel load beam of equivalent thickness. Stiffness can beregained if a stiffer material is substituted for the outer two sheetsof stainless steel. Such stiffer material can be a metal such as nickel,beryllium, rhodium or tungsten. If the load beam does not require aplastic forming procedure (such as stamping or punching) then ceramicmaterials such as silicon, alumina, or zirconia may be used.

The embodiments of the present invention described in detail above haveseveral advantages. One is that by separating the hinge portion from theload beam portion the sag and FAF can be independently controlled. Thisdesign independence allows the mass distribution to be altered byplacing ribs on the load beam such that the center of torsionalvibrations pass through the gimbal pivot point. This results in areduction of TMR in a disk drive. Another advantage of a suspensionaccording to the present invention is that the load beam can be formedfrom a material with much better vibration damping characteristics.While the invention has been shown and described with respect topreferred embodiments thereof, it will be understood by those skilled inthe art that changes in form and detail may be made in these embodimentswithout departing from the scope and teaching of the invention.Accordingly, the embodiments herein disclosed is to be considered merelyas illustrative, and the invention is to be limited only as specified inthe claims.

1. A method of forming a suspension for use in a disk drive having amedia disk, the method comprising: (a) pretreating a load beam withnickel to stiffen the load beam, reduce a weight of the load beam, andmatch a coefficient of thermal expansion of the load beam relative toconventional stainless steel load beams; (b) providing the disk drivehaving the media disk, an actuator for moving a slider relative to themedia disk, and a suspension extending from the actuator to the slider,the suspension having a hinge and the load beam that are formedseparately and welded together; (c) forming flanges on the load beamhaving flange cross-sectional shapes; and (d) forming ribs on the loadbeam having rib cross-sectional shapes that differ from the flangecross-sectional shapes, such that the ribs are different in structuralform than and spaced apart from the flanges.
 2. The method according toclaim 1, further comprising forming the flanges and the ribs on outeredges of the load beam.
 3. The method according to claim 1, furthercomprising inverting the flanges and ribs relative to each other suchthat the flanges are formed toward the media disk and the ribs areformed away from the media disk.
 4. The method according to claim 1,further comprising forming ends on at least one of the ribs, and forminga hole in the load beam at at least one of the ends of said at least oneof the ribs for stress relief of a material used to form the load beam.5. The method according to claim 4, further comprising forming a hole ateach end of each rib to define a plurality of holes in the load beam. 6.The method according to claim 1, further comprising selecting a materialused to form the load beam from the group consisting of metals,plastics, and ceramics.
 7. The method according to claim 1, furthercomprising selecting a material used to form the load beam from thegroup consisting of magnesium and magnesium rich alloys, and attachingthe load beam to the hinge by a method selected from the groupconsisting of adhesive bonding, diffusion bonding, and welding.
 8. Themethod according to claim 1, further comprising forming the load beamfrom a constrained layer damping material having two outer sheets ofmaterial selected from the group consisting of nickel, beryllium,rhodium, tungsten, and ceramics.
 9. The method according to claim 1,further comprising providing the load beam with a head gimbal pivotpoint and a torsional axis, and aligning the torsional axis with thehead gimbal pivot point.
 10. The method according to claim 9, whereinthe alignment is facilitated by forming the ribs on the load beam toredistribute a mass of the load beam and balance of a total mass of theload beam about the torsional axis.
 11. A method of forming a suspensionfor use in a disk drive having a media disk, the method comprising: (a)forming a load beam from a constrained layer damping material having twoouter sheets of material selected from the group consisting of nickel,beryllium, rhodium, tungsten, and ceramics; (b) providing the disk drivehaving the media disk, an actuator for moving a slider relative to themedia disk, and a suspension extending from the actuator to the slider,the suspension having a hinge and the load beam that are formedseparately and joined together; (c) forming flanges on the load beamhaving flange cross-sectional shapes; and (d) forming ribs on the loadbeam having rib cross-sectional shapes that differ from the flangecross-sectional shapes, such that the ribs are different in structuralform than and spaced apart from the flanges.
 12. The method according toclaim 11, further comprising forming the flanges and the ribs on outeredges of the load beam.
 13. The method according to claim 11, furthercomprising inverting the flanges and ribs relative to each other suchthat the flanges are formed toward the media disk and the ribs areformed away from the media disk.
 14. The method according to claim 11,further comprising forming ends on at least one of the ribs, and forminga hole in the load beam at at least one of the ends of said at least oneof the ribs for stress relief of a material used to form the load beam.15. The method according to claim 14, further comprising forming a holeat each end of each rib to define a plurality of holes in the load beam.16. The method according to claim 11, further comprising selecting amaterial used to form the load beam from the group consisting of metals,plastics, and ceramics.
 17. The method according to claim 11, furthercomprising selecting a material used to form the load beam from thegroup consisting of magnesium and magnesium rich alloys, and attachingthe load beam to the hinge by a method selected from the groupconsisting of adhesive bonding, diffusion bonding, and welding.
 18. Themethod according to claim 11, further comprising pretreating the loadbeam with nickel to stiffen the load beam, reduce a weight of the loadbeam, and match a coefficient of thermal expansion of the load beamrelative to conventional stainless steel load beams, and then weldingthe load beam to the hinge.
 19. The method according to claim 11,further comprising providing the load beam with a head gimbal pivotpoint and a torsional axis, and aligning the torsional axis with thehead gimbal pivot point.
 20. The method according to claim 19, whereinthe alignment is facilitated by forming the ribs on the load beam toredistribute a mass of the load beam and balance of a total mass of theload beam about the torsional axis.